#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int n, k;
  cin >> n >> k;
  if (n - k < 0) cout << 0 << endl;
  else cout << (1 << (n - k)) << endl;
  return 0;
}